This invention relates to locking flexible joint structures and fastener clips therefor, as well as to methods for making such clips.
Many joints, such as between modern furniture parts, are now fastened together by concealed mechanical connectors. Many of these concealed fasteners employ key hole-type slots and stud-like fasteners. Generally, this type of furniture fastening system includes short recessed areas along the edges of furniture members to be joined together. Fasteners or clips are mounted within the recessed areas of one furniture piece and studs are mounted on the other. The fasteners slidably engage the head of the studs in a slot, then seat the stud to firmly engage the separate furniture members.
In one prior form of such fasteners or clips, a flexible, rectilinear locking flange on the fastener is positioned so as to abut the stud when it is in a seated position. As the stud passes through the slot, the stud deflects the locking flange allowing the stud to reach its seated position. The locking flange then snaps back into position and thereby prevents the stud from being removed from the slot. Examples of such locking fasteners and furniture fastening systems are shown in U.S. Pat. No. 3,491,820 invented by E. J. Ostling, entitled FLEXIBLE JOINT STRUCTURE AND CLIPS THEREFOR, and U.S. Pat. No. 3,996,718 invented by R. M. Welch entitled FASTENING APPARATUS FOR PANELS. These fasteners function well and provide a permanent, yet concealed connection of furniture parts for environments which so require, such as in applications prone to vandalism.
Normally, this type of locking fastener clip is manufactured from a flat sheet metal blank in which the slot is cut, then the fastener bent to the desired configuration. Excess material which had previously filled the slot provides the locking flange. When so produced, the locking flange has the same configuration and width as the slot, with the exception that the end of the locking flange has been cut to a straight edge.
In certain applications, a slippage problem has been encountered with this prior type of locking fastener. When the joint formed by such a fastener is subjected to enough force or pressure, the locking flange is forced against the stud head in the slot. Continued pressure on the joint forces the locking flange to bend and slip along the side of the stud head toward the slot. Since the locking flange is the same width as the slot, the locking flange is pushed up through the slot and urged underneath the head of the stud in a wedge-like fashion, particularly when the fastener is used on a wood joint. This results in considerable play in the joint, and the joint is loose, sloppy and substantially weakened.
Accordingly, a need existed for a fastener clip and joint incorporating same which could withstand stresses and forces without slipping, loosening and/or weakening. However, it was desired that such clip not be complicated or expensive, be susceptible of rapid, mass production, yet be strong and durable.